Portable hand-held work apparatuses powered by internal combustion engines are well known in the art. When designing such apparatus, a high power-to-weight ratio is an important target. A limiting factor for increasing said ratio is the cooling capacity, which therefore needs to be improved.
Typically, the internal combustion engine is accommodated in an engine housing of the work apparatus and a crankshaft of the internal combustion engine is connected to a working tool via a suitable transmission mechanism. Further, the internal combustion engine directly or indirectly drives a fan wheel of a radial fan, which radial fan provides cooling of the internal combustion engine, especially by exposing cooling flanges of a cylinder of the internal combustion engine to a flow of cooling air. Typically, the fan wheel cooperates with a spirally-shaped fan housing surrounding the fan wheel. The fan wheel is mounted directly or indirectly to the crankshaft of the internal combustion engine and preferably, the fan wheel rotates at the same speed as the crankshaft. The fan wheel is configured to draw in air through its centre and blow air radially outwardly with the use of centrifugation.
Preferably, a combustion air inlet is located radially adjacent to the fan wheel and is used for leading combustion air to the internal combustion engine. Before reaching the internal combustion engine the combustion air flow passes an air filter. The position of the combustion air inlet radially adjacent to the fan wheel enables taking advantage of the centrifugal force acting on particles, e.g. dust particles, in the air flow, such that a purified air flow enters the combustion air inlet. Such use of centrifugation is often referred to as centrifugal purification. A purified combustion air flow reduces the risk of clogging of the air filter and can prolong service intervals. Clogging of the air filter is especially a problem in dusty environments. The air flow that does not enter the combustion air inlet is preferably used for cooling of the internal combustion engine, and especially for cooling the cylinder of the internal combustion engine. However, a problem with the described position of the combustion air inlet is that it is in the way of the flow of cooling air and, therefore, cooling capacity may be reduced.
Furthermore, a deflector can be provided downstream of the combustion air inlet and in close proximity to the periphery of the fan wheel. The deflector extends radially outwardly in relation to the fan wheel and ensures that the air flow is directed away from the fan wheel. This prevents air and particles from continuing to circulate with the fan wheel. Having air and particles staying in the radial fan will reduce cooling capacity, since the fan will then not be able to draw in as much air as desired. However, the deflector adds complexity to an overall construction of the radial fan and the work apparatus.